The present invention relates to a lightning arrester used for protection of transmission-distribution equipment subject to abnormal voltage.
Resistors having excellent non-linear resistive characteristic could be obtained by granulating a mixture of zinc oxide ZnO as a main component and small amounts of additive such as Bi.sub.2 O.sub.3, Co.sub.2 O.sub.4, Sb.sub.2 O.sub.3, MnO.sub.2 and CrO.sub.3, molding it and sintering it at about 1300.degree. C.
A non-dynamic current type lightning arrester can be formed by using said non-linear resistor as an element for lightning arrester since its resistance is infinite in the normal operation voltage.
Such lightning arrester need not have a serial gap whereby length of the lightning arrester can be shortened to less than 2/3 in comparison with a valve resistance arrester having serial gap and a compact structure of the lightning arrester can be given.
Such lightning arresters are disclosed in U.S. Pat. No. 3,806,765. As shown in U.S. Pat. No. 3,806,765, the non-linear resistor made of a main component of zinc oxide, is used by holding in an insulator. When a gap is formed between the non-linear resistor and an insulator, water is immersed into the insulator from outside and the non-linear resistor may be in wetting fault whereby satisfactory characteristic as the lightning arrester is lost. Therefore, a water sealing structure such as double O-ring packings is required between the insulator and terminals formed at both ends and the structure is complicated and quality control in a mass production is difficult.